Scaling out of CFD positions vs. full exits - your experience?

Been trading CFDs for a while now, mostly $DAX and $SPX. One thing I'm still figuring out is the best way to handle profitable trades. I often find myself taking full profit at the first sign of reversal, only to see the market continue in my original direction. I've read about scaling out, taking partial profits at various levels, but I'm struggling to implement it effectively. It feels like I'm leaving too much on the table, or conversely, my remaining position gets stopped out too often. For those who scale out of CFD positions, what's your typical methodology? Do you use fixed percentages at certain price levels, or is it more discretionary based on PA? And how do you manage the trailing stop for the remaining position?